Recently, growing concern has been expressed over the differential participation of boys and girls in high school mathematics courses. Because mathematics is a prerequisite for many college majors, limited mathematics background effectively precludes women from entering numerous career areas which include, but are not limited to, those in science and mathematics. In addition, we propose that the factors mediating the sex difference in mathematics participation reflect a more basic sense of lack of competence in females. Investigation of the determinants of one's decision to to take or not to take mathematics and of the precursors of females' underestimations of their abilities are the goals of this project. We have selected for study, variables that have been linked to choice in the expectancy/value model of behavior, i.e., one's expectancy for success and the incentive value of the task for the individual. In addition, several social factors are also identified as important in the development of expectancies for success and perceptions of the relative value of various behavioral options. Guided by this theoretical model, we designed a two year longitudinal cross-sectional project with three objectives: 1) the assessment of the relative importance of various intrapsychic factors in mediating differential participation rates in mathematics; 2) the identification of the developmental origins of individual differences on these intrapsychic variables; and 3) the plotting of the developmental emergence of these individual differences across the years from the fifth to the twelfth grade. To meet these goals, we gave students a battery of tests designed to measure individual differences on variables linked to expectancies and values, and a behavioral measure of learned helplessness. We observed teachers in the classroom and gave the teachers a comparable battery of measures designed to assess their expectancies and values both for themselves and for their students. Parents were given a similar battery to assess socialization in the home. By the use of cross-sequential and causal modeling analyses, the questionnnaire observation and behavioral measure data will prove the basis for meeting our three objectives.